Conventionally, in a semiconductor manufacturing apparatus such as a chemical vapor deposition (CVD) apparatus, a semiconductor film and an insulating film are formed on a wafer while heating the wafer by placing the wafer on a heating substrate of a stage heater provided in a vacuum chamber. The stage heater mentioned here includes: a heating substrate; and a shaft bonded to the back side of the heating substrate to support the heating substrate, wherein a heating element to heat the wafer is embedded in the heating substrate (refer to Patent Literature 1, for example).